Trouble Shooting

Uneven luster in locations where the material thickness varies.

Immediately after molten plastic has passed through a change in die thickness, factors such as the flow speed, cooling speed, and pressure applied to the die surface will change, and luster differs as a result of this.

• Raise the die temperature
• Increase molding temperature
• Increase the speed of the injection flow
• Raise the runners and gates
• Review the shaped of the molded component and round off corners on steps between areas of different thickness so that smoother flow may be realized.
  [Reference] Product design guide (thickness)

Apply colored ink to the die to ascertain the condition of flow mark occurrence.
Result of examining flow-mark start point as caused by level differences: The corner edge at the level-difference exit constitutes a start point for shear.

Striped patterns appearing in the area of gates

Plastic which has been cooled by sprues and runners is further cooled in the cavity and filling occurs at high viscosity; consequently, plastic in contact with the mold surface is pressurized in a semi-solidified condition and stripes perpendicular to the flow direction are formed on the surface of the molded product.

• Lower the setting for injection speed.
• Raise the injection pressure and hold pressure.
• Raise the temperature of the plastic and the die.

This flow-mark pattern is characterized by alternating areas of glossy and cloudy plastic.

This type of flow mark is caused by unstable flow at the flow front.

• Lower the setting for injection speed.
• Raise the temperature of the plastic and the die.